Inadequate Sleep Undermines Dietary Fat Loss

Dieting sometimes just doesn’t work out as hoped, despite your best intentions. Before you reexamine your exercise routine or diet, consider your sleeping habits.

A small study conducted at the University of Chicago suggests sleep is the third vital element in the battle to shed fat. Exercise and dietary efforts may be less effective without a regular 7-8 hours of shuteye.

Dieters in the study shed the same amount of weight with less sleep, however when they had adequate sleep they burned off more body fat. An abstract is available on the website of the journal Annals of Internal Medicine.

A group of 10 overweight study participants with an average BMI of 27.4 adopted a diet with 90 percent of calories required to maintain weight without exercise. The volunteers dieted in two 14-day intervals. One involved sleep restriction with only 5.5 hours per night compared to 8.5 hours in the control portion of the study.

The subjects lost an average of 6.6 lbs during each 14-day dieting period. Half of the weight lost was body fat with adequate sleep. In the sleep restriction condition, the dieters lost only 1.3 lbs of fat and 5.3 lbs of lean body mass.

They also felt hungrier. The “hunger hormone” Ghrelin increased during sleep loss, causing a spike in appetites. Ghrelin also promotes the retention of fat, the study authors report.

"If your goal is to lose fat, skipping sleep is like poking sticks in your bicycle wheels," said Plamen Penev, MD, PhD, the study’s principal investigator. “One should not ignore the way they sleep when going on a diet.”

The authors intend to further investigate how sleep loss affects diet results. They plan on conducting similar, lengthier studies with larger samples of dieters.